Differential isoform expression of Allergin-1 during acute and chronic inflammation

Immun Inflamm Dis. 2022 Dec;10(12):e739. doi: 10.1002/iid3.739.


Introduction: Neutrophils are crucial to antimicrobial defense, but excessive neutrophilic inflammation elicits immune pathology. Currently, no effective treatment exists to curb neutrophil activation. However, neutrophils express a variety of inhibitory receptors which may represent potential therapeutic targets to limit neutrophilic inflammation. Indeed, we previously showed that the inhibitory collagen receptor leukocyte-associated immunoglobulin-like receptor 1 (LAIR-1) regulates neutrophilic airway inflammation and inhibits neutrophil extracellular trap formation. The inhibitory receptor Allergin-1 is expressed by myeloid cells and B cells. Allergin-1 suppresses mast cell and basophil activation, but a potential regulatory role on neutrophils remains unexplored. We aimed to demonstrate the regulation of neutrophils by Allergin-1.

Methods: We examine Allergin-1 isoform expression on human neutrophils during homeostatic (healthy donors) and chronic inflammatory (systemic lupus erythematosus patients) conditions in comparison to other circulating leukocytes by flow cytometry. To reveal a potential role for Allergin-1 in regulating neutrophilic inflammation, we experimentally infect wild-type (WT) and Allergin-1-deficient mice with a respiratory syncytial virus (RSV) and monitor disease severity and examine cellular airway infiltrate. Flow cytometry was used to confirm Allergin-1 expression by airway-infiltrated neutrophils in RSV infection-induced bronchiolitis patients.

Results: Only the short 1 (S1) isoform, but not the long (L) or S2 isoform could be detected on blood leukocytes, with the exception of nonclassical monocytes, which exclusively express the S2 isoform. Allergin-1 expression levels did not vary significantly between healthy individuals and patients with the systemic inflammatory disease on any interrogated cell type. Airway-infiltrated neutrophils of pediatric RSV bronchiolitis patients were found to express Allergin-1S1. However, Allergin-1-deficient mice experimentally infected with RSV did not show exacerbated disease or increased neutrophil airway infiltration compared to WT littermates.

Conclusion: Allergin-1 isoform expression is unaffected by chronic inflammatory conditions. In stark contrast to fellow inhibitory receptor LAIR-1, Allergin-1 does not regulate neutrophilic inflammation in a mouse model of RSV bronchiolitis.

Keywords: inhibitory receptor; neutrophils; nonclassical monocytes; respiratory syncytial virus; systemic lupus erythematosus.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Animals
  • Bronchiolitis*
  • Child
  • Humans
  • Inflammation* / genetics
  • Inflammation* / metabolism
  • Mice
  • Neutrophils
  • Protein Isoforms / genetics
  • Receptors, Immunologic* / genetics
  • Receptors, Immunologic* / metabolism
  • Respiratory Syncytial Virus Infections* / genetics
  • Respiratory Syncytial Virus Infections* / metabolism
  • Respiratory Syncytial Viruses


  • MILR1 protein, human
  • Protein Isoforms
  • Receptors, Immunologic